I am new to owning my S2k, and I love the car. But there is one discomfort with the car. If it is normal then I won't worry about it, otherwise warranty time! My S2k is a 2000 with 24k. I am getting a loud resonance sound (humming rattle) under deceleration. Example, I am cruising at 65 and decelerate, at first I get the normal exhaust sound, then @ about 2500 RPMs the resonance gets loud, and sounds like a humming rattle. Is this normal? Or is my stock exhaust rotted out? Any help is apreciated

 

Hard to tell from the description... but they do have a almost buzzy sound from the headers... that's kinda normal.

 

I believe you have the well known clutch decel buzz. Honda has a TSB for this but you have a MY'00 and it's up to your dealer to decide whether or not to fix it. It's the clutch springs vibrating as a result of gear backlash in the tranny. Mechanically, it's no big deal - only a noise. Many of the cars that got the TSB fix have had the buzz return almost immediately.
Go to the S2Ki.com home page and you'll find tabs to take you to the TSBs. One of them involves this issue.